1.往集合中插入一个文档
	db.users.insert(
	{id:19,name:"limu",age:28}
	)
2.查询集合中所有文档
	db.users.find(
	{}
	)
3.把一个带有name=limu的文档，修改其age值为30
	db.users.update(
	{name:"limu"},
	{$set:{age:30}},
	{multi:true}
	)
4.//修改所有name=limu的文档，修改其name=bunny，age=20
	db.users.updateMany(
		{name:"limu"},
		{$set:{name:"bunny",age:20}}
	)
5.修改所有的文档，修改其name=xxx，age=10
	db.users.updateMany(
	{},
	{$set:{name:"Xxx",age:10}}
	)
6.添加一个sex的列
 db.users.updateMany(
 {},
 {$set:{sex:""}}
 )
7.删除sex的列
	db.users.updateMany(
	{},
	{$unset:{sex:""}}
	)
8.//删除_id=5f255a938d570000440072fe的文档
	db.users.remove(
	{_id:ObjectId("5f255a938d570000440072fe")},
	{justOnly:true}
	)

9.//删除所有带有name=dafei的文档
	db.users.deleteMany(
	{name:"dafei"}
	)
	
	db.users.remove(
	{name:"dafei"},
	{justOnly:false}
	)
10.//删除当前数据库中所有文档
	db.users.deleteMany(
	{}
	)
	
db.users.insert({"id":NumberLong(1),"name":"dafei","age":NumberInt(18)})
db.users.insert({"id":NumberLong(2),"name":"xiaofei","age":NumberInt(20)})
db.users.insert({"id":NumberLong(3),"name":"zhang quan dan","age":NumberInt(33)})
db.users.insert({"id":NumberLong(4),"name":"zhang kun","age":NumberInt(26)})
db.users.insert({"id":NumberLong(6),"name":"cai xv kun","age":NumberInt(29)})
db.users.insert({"id":NumberLong(7),"name":"jia nai liang","age":NumberInt(25)})
db.users.insert({"id":NumberLong(8),"name":"fu rong wang","age":NumberInt(28)})
db.users.insert({"id":NumberLong(9),"name":"wang da","age":NumberInt(31)})
db.users.insert({"id":NumberLong(10),"name":"da wang","age":NumberInt(32)})
db.users.insert({"id":NumberLong(11),"name":"will","age":NumberInt(26)})
	
11.查所有用户
	db.users.find(
	{}
	)
12.查询所有用户按年龄排序(正序/倒序)
	db.users.find({}).sort({age:1})
	db.users.find({}).sort({age:-1})
13.查询所有用户按年龄和id排序(多列排序)
	db.users.find({}).sort({age:1,id:-1})
14.按照年龄降序排列，查询第2页，每页显示3个
	db.users.find({}).sort({age:-1}).skip(3).limit(3)
15.查询age > 30的用户
	db.users.find(
	{age:{$gt:30}}
	)
16.查询名字为 dafei 或xiaofei用户
	db.users.find(
	{
		name:{$in:["dafei","xiaofei"]}
	}
	)
17.判断指定name列是否存在
	db.users.find(
		{name:{$exists:true}}
		)
18.查年龄在28 到 30间的用户信息
	db.users.find(
	{
		$and:[{age:{$gte:28}},{age:{$lte:30}}]
	}
	)
	
	db.users.find(
	{
		age:{$gte:28,$lte:30}
	}
	)
19.查看年龄小于28或者年龄大于30用户信息
	db.users.find(
	{
		$or:[{age:{$lt:28}},{age:{$gt:30}}]
	},
	{
		name:1,_id:0
	}
	)
20.查看年龄等于28或者等于30用户信息
	db.users.find(
	{
	age:{$in:[28,30]}
	}
	)

21.查询name带有fei的用户信息
	db.users.find(
	{
		name:/fei/
	}
	)
22.查name中包含fei字样，并且年龄在28 到 30间的用户信息,
	db.users.find(
	{
		$and:[{name:/fei/},{age:{$gt:28}},{age:{$lt:30}}]
	}
	)
数组操作 

23.给所有的数据添加数组字段hobby
	db.users.update(
	{},
	{$set:{habby:[]}},
	{multi:true}
	)
24.给name等于dafei的用户添加java 爱好
	db:users.update(
	{name:"dafei"},
	{}
	)
25给数组habby字段添加数据， 不允许数据元素重复
	db.users.update(
	{name:"dafei"},
	{
		$push:{habby:"java"}
	}
	)
26.给name等于dafei的用户添加'java', 'c', 'vue' 爱好
	db.users.update(
	{name:"dafei"},
	{$addToSet:{habby:{$each:["java","c","vue"]}}}
	)
27.需求删除name=dafei用户最后一个兴趣
	db.users.update(
	{name:"dafei"},
	{$pop:{habby:1}}
	)
28.需求删除name=dafei用户第一个兴趣
	db.users.update(
		{name:"dafei"},
		{$pop:{habby:-1}}
	)
29.删除name=dafei用户java兴趣选项
	db.users.update(
	{name:"dafei"},
	{$pull:{habby:"java"}}
	)
30将name=dafei的用户索引为1的兴趣改为 go
	db.users.update(
	{name:"dafei"},
	{
	$set:{"habby.1":"go"}
	}
	)
31.将name=dafei的用户 c 兴趣 改为 c#
	db.users.update(
	{name:"dafei",habby:"c"},
	{
		$set:{"habby.$":"c#"}
	}
	)
